Cathode-ray and other vacuumized tubes resistant to violent devacuation



E. POWELL ETAL CATHODE-RAY AND OTHER VACUU 3,403,805 MIZED TUBES Oct. 1,1 968 RESISTANT TO VIOLENT DEVACUATION 2 Sheets-Sheet 1 Filed May 31,1966 INVENTOR.

PEAR 69%! D. E. POWELL ETAL 3,403,805 CATHODE-RAY AND OTHER VACUUMIZEDTUBES Oct. 1, 1.968

RESISTANT TO VIOLENT DEVACUATION 2 Sheets-Sheet 2 Filed May 31, 1966 flm o INVENTOR. DE Po WELL BM) PEAK United States Patent 3,403,805CATHODE-RAY AND OTHER VACUUM IZED TUBES RESISTANT T0 VIOLENT DEVACUATIONDaryl E. Powell, Maumee, and Burton W. Spear, Toledo, Ohio, assignors toOwens-Illinois, Inc., a corporation of Ohio Filed May 31, 1966, Ser. No.553,757 13 Claims. (Cl. 2202.1)

ABSTRACT OF THE DISCLOSURE A direct-viewing impolsion resistantcathode-ray television picture tube comprising a glass envelope having afunnel portion and a flanged face plate member. An annular perforatedreinforcing band is closely fitted to the external surface of the faceplate flange. The perforations in the band are filled with a singlelayer of adhesive material which also extends under the band to form anintermediate layer between the band and the surface therebeneath.

The present invention relates to cathode-ray tubes and more particularlyto the control and prevention of fracture and implosive-explosiveeffects in vacuumized cathode-ray picture tubes for televisionreception. More specifically, this invention relates to improved typesof directviewing cathode-ray image tubes having glass envelopes andmethods of fabricating such envelopes to eliminate breakage and tocontrol devacuation thereof either in processing, shipping, installationor while in service.

Cathode-ray tubes are vacuumized to very low pressure and breakage ofthe envelope for any reason usually results in an implosion. Suchimplosion is accompanied by an explosion which, particularly in the caseof large size envelopes, can be damaging where fragments of the envelopeare projected in random directions with considerable force. The mostcommon solution to this problem for many years has involved the use of atempered-glass implosion panel mounted in front of the tube face plate.Such glass panel mounted in the front of television receiver cabinet andthe cabinet itself have been relied upon to contain implosion-explosioneffects. In more recent years, the television industry has adopted anintegrallysafe direct-viewing tube envelope and it is this type of tubestructure that the present invention is concerned.

US. Patent Nos. 3,220,592 and 3,220,593 which issued in our names onNov. 30, 1965, relate to a basic type of direct-viewingimplosion-resistant cathode-ray television picture tubes having glassenvelopes and methods of fabricating such tube envelopes. Theseinvention eliminate sources of fracture originating in highly-stressedareas and particularly those of substantially maximum cross-sectionaldimensions of the envelope and prevent the deleterious effects whichresult from sudden violent devacuation.

-As disclosed in the referenced patents, noteworthy results have beenachieved in protecting non-viewing areas of the tube envelope in suchmanner that damage to the tube envelope from whatever source andwherever caused cannot result in damaging implosion-explosion. The needfor a separate implosion plate either mounted separately from orintegrally with the image tube face plate has been eliminated in suchmanner that the tube face plate may be direct-viewing in allconventional sizes of television picture tubes.

The present invention constitutes an improvement over the tubeconstructions and methods of fabricating disclosed in the referencedpatents, particularly with regard to further reducing the likelihood ofan implosion and preventing its occurrence as well as providing improvedreinforcement at minimal cost.

Accordingly, it is an object of the present invention to provide adirect-viewing cathode-ray tube construction which is capable ofexpeditious fabrication to provide both resistance to fracture andcontrol of sudden devacuation without serious fragmentation of theenvelope under widely-varying adverse conditions.

Another object of this invention is to provide an improved type ofessentially all-glass cathode-ray tube envelope by the use of annularreinforcing elements mounted on non-viewing exterior surfaces of theenvelope at peripheral sidewall areas which are subject to damage due totheir dimensions with such elements controlling sudden devacuation uponfracture however caused.

Another object of this invention is to provide a directviewingnon-imploding cathode-ray image tube construction which may be directlyviewed without a protective implosion panel mounted forwardly of itsviewing area, such construction being applicable to resisting commonforms of glass surface damage in both large and small size tubes andpreventing their violent devacuation, the internal working components ofthe completed tube being fully capable of functioning in their normalmanner.

A further object of this invention is'to provide a cathode-ray tubestructure having an essentially all-glass tube envelope with an annularperforated metal reinforcing band surrounding its forwardmostnon-viewing sidewalls surrounding its viewing screen, said band beingadaptable to mounting on either round or rectangular envelopes eitherbefore or after their final fabrication into completed tubes.

A still further object of this invention is to provide a method ofimparting fracture resistance to a rectangular glass cathode-ray tubeenvelope to eliminate implosiveexplosive effects on breakage of theenvelope from any cause. Fracture propagation through an annular area ofmaximum cross-sectional dimensions is prevented or retarded in suchmanner that violent collapse of major sidewalls of the envelope cannotoccur. 7

The specific nature of this invention, as well as other objects andadvantages will become apparent to those skilled in the art from thefollowing detailed description taken in conjunction with the annexedsheets of drawings on which, by way of preferred example only, areillustrated of the preferred embodiments of the invention.

On the accompanying drawings:

FIG. 1 is a perspective view of a cathode ray television picture tubefabricated in "accordance with the present invention.

FIG. 2 is an enlarged vertical sectional view of one portion of the tubeenvelope taken along the line of 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 2 showing another embodiment of theinvention.

FIG. 4 is a perspective view similar to FIG. 1 showing still anotherembodiment of the invention.

FIG. 5 is an exploded view illustrating the individual componentsutilized to form the embodiment shown in FIG. 4.

FIG. 6 is an enlarged vertical sectional view of one portion of the tubeenvelope taken along the line 66 of FIG. 4.

FIG. 7 is an enlarged fragmentary view showing a modification of theinvention illustrated in FIGS. 1 and 2.

The present invention is described hereinafter as specifically appliedto the manufacture of cathode-ray television picture tubes. However, itwill be apparent to those skilled in the art that the invention isequally applicable to the manufacture of many different types of vacuumtubes utilizing glass envelopes, particularly those having substantialdimensions which are subject to implosion and virtually simultaneousexplosion on sudden devacuation.

The term devacuation as used herein is intended to mean the converse ofvacuation as in the case where a vacuumized vessel or tube experiencesan internal pressure change toward atmospheric upon loss of vacuum. Therate of change may occur rapidly, in which case the deleterious effectscan be exceedingly violent, or more slowly over a longer period of timewhereby such effects are greatly moderated. Obviously, moderating therate of devacuation results in gradual dissipation of the forcescausative of destructive implosion.

The present invention provides an implosion-resistant system which iscapable of being incorporated into all existing types and shapes ofconventional cathode-ray picture tubes without serious alteration ormodification of present fabricating procedures. The invention may beincorporated into any selected type of tube using materials and methodswhich are capable of supplementing normal bulb and tube production. Theterm bulb is applied to hollow glass envelopes having none of theimage-producing electrical components installed While the term tube isused to designate the completed electron-discharge device having all ofits electrical components installed in fully-evacuated condition,capable of displaying a raster on its image-creating screen.

In a preferred embodiment of the present invention, a glass cathode-raytube envelope is normally comprised of a funnel member 11, face platemember 12 and neck tubulation 13 which are joined to form a unitaryhollow glass article capable of withstanding the force of atmosphericpressure when vacuumized. The terminating end of neck tubulation 13 isnormally sealed by an end cap 14 retaining one or more electronbeam-emitting guns which project forwardly interiorly through necktubulation 13. Funnel member 11 is usually frusto-conical orfrustopyramidal in shape with its smaller end sealed to neck 13 and itslarger end sealed to face plate 12 at a planar seal line 15.Electromagnetic beam-deflecting coils (not shown) are normallyexteriorly mounted at the yoke area where neck 13 and funnel small endare joined to provide proper scanning of the tube screen 16 by theelectron beam.

Face plate 12 consists of a concavo-convex viewing portion 12a bounded'by a depending annular side panel or flange 12b. Flange 12b and funnellarge end terminate in annular sealing surfaces of complemental contour.The sealing surfaces are joined at seal line either by direct fusion ofthe glass or by an interposed annular layer of low-melting glass-sealingcomposition such as a devitrifying-type solder glass which is selectedas being compatible with the thermal and physical characteristics of theparent glass parts. The basic shape of the envelope viewing area 12a maybe either circular or rectangular in plan as conventionally known in theart with the sealing surfaces being substantially planar for forming adurable hermetic joint. The foregoing description is applicable to manyknown types of television picture tubes used for both monochromatic andpolychromatic image creation.

The invention, as presently contemplated, consists of applying selectedelements to external non-viewing surfaces of the tube envelope, eitherafter the tube is fully fabricated or prior to subjecting the envelopeor bulb to a tube fabricating process. In the former case the tubeisfully completed and assembled with all its required external andinternal working components properly installed in operative alignmentand after being subjected to bake-out temperatures and devacuation. Inthe latter case, the tube envelope consists of the so-called glass bulbhaving only a part of the electronic working components installed suchas the metal anode button in the funnel side wall and/ or a plurality ofmask mounting studs sealed internally of face plate flange 12b in thecase of a color TV envelope. The envelope or bulb is subjected to theapplication of the required elements with ambient conditions existingboth exteriorly and interiorly thereof. The bulb, after being fabricatedinto a form Where its devacuation can be controlled, is then subjectedto a tube fabricating process. In this case, the components of thepresent implosion resistant system must be capable of withstandingrequired bake- 4- out cycling temperatures and pressures of the tubemaking process.

In describing a preferred embodiment of the present invention shown inFIGS. 1 and 2, a completed picture tube 10 capable of recreatingtransmitted images is subjected to reinforcement of the tube envelope inthe following manner:

An annular perforated reinforcing band 20 of thinwalled high-tensilestrength material such as metal is press formed having a transversecross-sectional contour which conforms snugly to the forwardmostnon-viewing exterior surfaces of face plate flange portion 12b. Band 20preferably consists of preformed shaped metal member having a pluralityof spaced-apart perforations or apertures 21 extending throughout itslateral and circumferential dimensions. Band 20 is preferably formed ofpressed sheet steel having a thickness of about .020 to .040 inch whichis capable of surrounding and encompassing the non-viewing corner regionof the face plate closely adjacent its viewing area. Band 20 may consistof either an untensioned rim band or a tension band depending upon thesize and shape of the tube envelope.

In the illustrated embodiment of the invention shown in FIGS. 1 and 2,the concavo-convex character of rectangular viewing area 12a of the faceplate is shown which is utilized in many conventional types ofcathode-ray picture tubes. Rim band 20 has a substantially greater widthat the center of its arcuately-shaped long axis sides and lesser Widthon its similarly-shaped short axis sides. The forward edge ofreinforcing rim band 20 has a contour which is similar in shape to theperiphery of the envelope screen line and the rearward edge resides in aplane normal to the tube axis and parallel to the mold match line of theface plate flange. Mold match line 120 is a region of maximalcross-sectional dimensions of the envelope.

Perforated rim band 20 is preferably formed with a circumferentialdimension which is closely fitted to the external surfaces of the faceplate flange. Band 20 may be formed from two U-shapedsymmetrically-similar half sections which are welded together to form anendless band or it may be press-formed from a single sheet of perforatematerial. After the band is properly formed in foreshortened condition,it is expanded such as by heating and placed over and around theexterior surfaces of the face plate flange which may or may not bepreheated as required. Normally preheating of the face plate or theentire bulb is not required; however, some slight preheating may bedesirable in some cases to prevent thermal shock. Band 20 is permittedto cool in place to contact around the surrounded exterior surfaces sothe band develops tensile stresses which in turn develop counteractingcompressive stresses in the glass sidewalls therebeneath. Such sweatingon of band 20 is most effective when the band is preheated to anelevated temperature short of damaging effects to enlarge the same dueto thermal expansion and the bulb remains unheated.

Following application of band 20 perforations 21 in the rim band whichare complete apertures are preferably filled with a single layer ofadhesive material such as low-melting solder glass to essentially fillthe perforations and extend under the band to forman intermeditte layerbetween band and exterior surfaces therebeneath. The intermediate layerof adhesive material may or may not extend fully annularly. It isadequate for the intended purposes if it cements band 20 in place onlyin localized areas throughout the face flange periphery. A preferredsolder glass is a lead-zinc-borate devitrifying-type sealing glasscomposition similar to Owens-Illinois Product No. CV- may be used toprovide an intermediate layer 30 of adhesive or sealing material. Wheresolder glass is employed as the adhesive, its thermal expansioncoeflicient is preferably matched to band 20 such as stainless steel No.430 to permit its being applied either prior to or after bandapplication.

As an alternative, intermediate layer 30 of adhesive material maybecomprised of a synthetic organic resinous material such as epoxy orpolyester resin. The epoxy resin for example consists of a thermosettingsynthetic resin having the ability to chemically bond to both the metaland glass surfaces with the material having good chemical resistance andsufficient flexibility to permit some flexure of the bond withoutdestruction. The epoxy system is composed of liquid epoxide resin whichis cross linked by a liquid hardener into a thermoset which is a tough,resistant solid having excellent dimensional stability and strength.Such reacted resin system when cured forms a stable firmly-adhesive bondto both the, glass and metal. A preferred material consists of a DowEpoxy Resin No. 741 manufactured by Dow Chemical Company which has beenpreviously heated to a temperature ranging from 170 to 190, the resinhaving been previously mixed with eight parts of Dow Epoxy ResinHardener No. 61 per one hundred parts of resin. An example of polyesterresin is Plaskon Polyester Resin No. 9407 which is a rigid type,promoter-containing resin to which a catalyst such as methyl ethylketone peroxide is added to initiate tack-free cure.

Thus, it can be seen from the construction shown in FIGS. 1 and 2, rimband 20 may be applied either to an unexacuated bulb or completed tube;however, selection of the adhesive material must take into considerationits ability to withstand elevated temperatuers of the order of 430 C.which are utilized in tube bake-out cycling if a tube making operationis to follow. The form of the invention shown in FIGS. 1 and 2 is ofspecial advantage in reinforcing smaller size picture tubes of the orderof 11, 12, and 16 diagonal inch sizes.

In another embodiment of the present invention shown in FIG. 3, the rimband 20a consists of a semi-annealed steel strap having a uniformcross-section with a series of perforations or apertures 21a formedthroughout its circumferential and lateral extent. Such band preferablyconsists of semi-annealed steel strapping of substantially uniformrectangular cross-section which is capable of being placed in tensionand is particularly useful .for surrounding the skirt portion of smallpicture tube sizes such as 11 and 12 diagonal inch. In such sizes,flange 12b has lesser dimensions and adequate implosion protection canbe provided by such band properly applied. Band 20 a is positioned sothat its centerline preferably coincides with mold match line 120 of theface flange portion. p

In another modified form of the invention shown in FIG. 7, perforate rimband 20b is essentially enveloped by an annular layer 30b of low-meltingsolder glass or synthetic resin 30b. In this case, the layer of solderglass 30b contacts both interior and exterior surfaces of the perforatedrim band. and is applied to a greater extent both internally andexternally of the rim band to obtain improved adherence of the rim bandto the glass exterior surfaces. The perforate nature of the band and itsenveloping layer of adhesive material permit their ready application toa wide range of types of picture tubes with good results, especiallysmaller sizes.

.In a still further embodiment of the present invention, FIGS. 4, 5 and6 illustrate a contoured perforate or mesh-type rim band 200 which isapplied in the same manner as described hereinabove. Band 200 ispreferably placed in tension by shrink fitting the same onto the tube;however, it may be untensioned. After the rim band is mounted in place,a second reinforcing band is applied over and around the rearward edgeof rim band 20 forwardly of envelope seal line 15. Band 40 consists ofhigh-tensile strength material such as semi-annealed steel strappingwhich is essentially imperforate and is termed a tension band. Aconnecting clip 41 is fitted onto one end of tension band 40 for joiningits ends and maintaining continuous tension. Rim band 200 r ispreferably overlapped to approximately one-half the width of tensionband 40. The selected adhesive material 30 is then applied to theexterior surface of band 200 to penetrate its apertures and to flow atleast in localized areas into the space between rim band 200 and theglass exterior surfaces.

In each of the embodiments of the invention described above, a plasticor rubber-like material may be used in place of metal for perforated rimband 20'; however, the latter affords the optimum degree ofreinforcement. Also the development and maintenance of permanent tensilestresses can be better controlled with a metal band. By proper controlof the stresses imparted into the glass sidewalls, the eifect of asource of fracture and resultant breakage is controllable to a highdegree.

The following Table I sets forth devacuation data for a series of 5foot-pound impact tests for evacuated 12 inch bul-bs protected inaccordance with the present invention as shown in FIG. 3. In each ofthese tests, a thin coating of Saureisen cement was first sprayed on theface rim area.12b to protect the glass against thermal shock duringthesweating-on application of the hot perforated band. Followingapplication of the perforated band, the Saureisen cement was appliedover the band and made spot contact with the glass through theperforations. If desired, the Saureisen cement may be modified with afiller material to lower its thermal expansion coefiicient. Thefollowing results employed Saureisen cement and 50% filler material suchas fine particle perlite, althrough the former used alone provides goodresults.

In a series of twenty-two (22) tests, ten (10) of which arerepresentative and shown in the table, no cave-ins of the envelope orfunnel implosions whereby the funnel portion collapses were experienced.Also, no glass fragments were thrown beyond three (3) feet in any of thetests. Total glass fallout dropped immediately in front of the testcabinet averaged only 1% ounces for the twenty-two (22) tests, all inthe form of small fragments.

This data is representative of only one embodiment of the invention asillustrated by FIG. 3 of a uniform cross-section tension-band with theaddition of the adhesive over the top of the band as illustrated in FIG.7.

Examples of results obtained by implosion testing a series ofcathode-ray picture tubes utilizing the stated conditions are asfollows:

TABLE I Distance (ft.) Band Short- Ball Weight Impact Impact Test No.Band Size ene d D(i me5n- Obs.) (ft.-lbs.) position Result 0-8 3-5 5sion in.

' Glass Throw (ozs.)

.020 1% 5 Front Large Hole O 0 .020" 1% 5 d 0 0 .020" .150 1 5 1 0 0.020" .150 1% 5 0 0 0 .020- 1% 5 1 0 0 .020"- 200 1% 5 2 0 0 023" 025 1%5 0 0 0 023 .075 1% 5 5% 0 0 023 .125 1% 5 0 O 0 023" 175 1% 5 0 0 0What is claimed:

1. A direct-viewing implosion-resistant television picture tube envelopecomprising a substantially funnelshaped hollow body portion and alight-transmitting viewing portion enclosing its larger end, saidviewing portion having an integral peripheral sidewall region ofsubstantially maximum cross-sectional dimensions of said envelope sealedto the larger end of said body portion,

an endless reinforcing band of thin-walled high-tensile strength metalsurrounding the non-viewing peripheral sidewall region of said viewingportion and complementally contoured to conform snugly thereto,

a plurality of small perforations formed in said reinforcing bandextending both laterally and circumferentially essentially throughoutits dimensions,

adhesive means penetrating into the perforations of said reinforcingband and contacting the envelope exterior surfaces therebeneath bondingsaid band thereto, and

constricting means surrounding at least one annular portion of saidreinforcing band to maintain the same in closely conforming relationwith respect to the peripheral sidewall region,

said reinforcing band, adhesive means and constricting meansconjunctively having sufficient yield strength to maintain the envelopesidewall region therebeneath intact upon breakage of said envelope.

2. A direct-viewing implosion-resistant television picture tube envelopein accordance with claim 1, wherein said constricting means comprises asecond reinforcing band of thin-walled high-tensile strength metal ofuniform cross-section maintained in continuous tension disposed aroundthe rearward portion of said first reinforcing band and substantiallyforward of said envelope body portion.

3. A direct-viewing implosion-resistant television picture tube envelopein accordance with claim 1, wherein said reinforcing band comprises apair of complemental U-shaped half-sections of thin-walled high-tensilestrength metal disposed in telescoping relation around the forwardmostnon-viewing peripheral sidewall region of said envelope, said band beingconcave-convex in transverse cross-section to conform to the envelopeexterior surfaces at said envelope sidewall region.

4. A direct-viewing implosion-resistant television picture tube envelopein accordance with claim 1, wherein said plurality of small aperturescomprises a series of uniform circular openings disposed in spaced arraythroughout all areas of said reinforcing band.

5. A cathode-ray tube envelope resistant to fracture and capable ofcontrolled devacuation on breakage comprising a substantiallyfunnel-shaped hollow body portion and a light-transmitting viewingportion enclosing its larger end, said viewing portion having anintegral peripheral sidewall region of substantially maximumcrosssectional dimensions of said envelope sealed to the larger end ofsaid body portion,

an annular reinforcing band of thin-walled high tensile strengthmaterial surrounding the peripheral sidewall region and complementallycontoured to conform snugly thereto,

a plurality of perforations comprising a series of apertures extendingsubstantially throughout the lateral and circumferential extent of saidreinforcing band,

adhesive means penetrating and essentially filling the said series ofapertures in said band thereby bonding said band directly to theexterior surfaces of said peripheral sidewall region,

said reinforcing band and intermediate adhesive means having sufficientyield strength to substantially prevent fracture propagation through theenvelope sidewall region therebeneath upon breakage of said envelope.

6. A cathode-ray tube envelope in accordance with claim 5, wherein saidannular reinforcing band comprises a one-piece thin-walled high-tensilestrength metal memher having a uniform transverse cross-section, exceptfor the perforations.

7. A cathode-ray tube envelope in accordance with claim 5, wherein saidannular reinforcing band comprises a one-piece thin-walled high-tensilestrength metal member having a non-uniform concavo-convex transversecross-section complemental to the forwardmost nonviewing exteriorsurfaces of said envelope.

8. A cathode-ray tube envelope in accordance with claim 5, wherein saidadhesive means comprises an intermediate layer of epoxy resin containingmaterial in solidified reacted condition.

9. A cathode-ray tube envelope in accordance with claim 5, wherein saidadhesive means comprises an intermediate layer of low-melting solderglass having a thermal expansion coefiicient complemental to saidenvelope and reinforcing band.

10. The method of protecting an essentially all-glass cathode-ray tubeenvelope against fracture and implosiveexplosive elfects upon suddendevacuation comprising the steps of mounting an annular perforatereinforcing band of thin-walled high-tensile strength material aroundthe peripheral sidewall region of substantially maximum cross-sectionaldimensions of said envelope, said band having a plurality of aperturesextending substantially throughout its lateral and circumferentialextent,

introducing an annular layer of adhesive material intermediate saidreinforcing band and the sidewall surfaces therebeneath to substantiallyfill the apertures of said band, said adhesive material having a thermalexpansion coefficient complemental to said envelope and said reinforcingband, and

curing said adhesive material to bond said band to the envelope exteriorsurfaces therebeneath.

11. The method in accordance with claim 10, including the steps ofexpanding an endless perforate metal reinforcing band havingcircumferential dimensions and contour closely complemental to saidenvelope peripheral sidewall region,

applying the expanded metal band to the forwardmost non-viewing sidewallregion of said envelope, and contacting said band to place the same incontinuous tension.

12. The method in accordance with claim 10, including the step ofintroducing epoxy resin containing material in an annular pattern intothe perforations of said reinforcing band to contact the envelopeexterior surfaces therebeneath to band the same into an integralstructure capable of preventing fracture propagation therethrough uponbreakage of said envelope.

13. The method in accordance with claim 10, including the step ofintroducing a layer of low-melting solder glass in an annular patterninto the perforations of said reinforcing band to contact the envelopeexterior surfaces therebeneath.

References Cited UNITED STATES PATENTS 2,969,163 1/1961 Roberts 220 2.33,162,933 12/1964 Trax et al. 2202.1 3,314,566 4/1967 Minneman et al.220--2.1

MARTHA L. RICE, Primary Examiner.

